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A297195 Number of bitriangular permutations (row sums of A272644 if that triangle is prefixed with a row for n=1). 2
1, 1, 2, 7, 28, 133, 726, 4483, 30896, 235105, 1957930, 17712799, 172980804, 1813760317, 20323234814, 242353047355, 3064550705752, 40958281206169, 576917769130578, 8541793624670551, 132623408805525740, 2154730841214003061, 36560670776303600422, 646697046042017004787 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..24.

Irving Kaplansky and John Riordan, The problem of the rooks and its applications, Duke Mathematical Journal 13.2 (1946): 259-268. The array is on page 267.

Irving Kaplansky and John Riordan, The problem of the rooks and its applications, in Combinatorics, Duke Mathematical Journal, 13.2 (1946): 259-268. [Annotated scanned copy]

MAPLE

A297195 := proc(n)

    if n = 1 then

        1;

    else

        add(A272644(n, m), m=1..n-1) ;

    end if;

end proc:

seq(A297195(n), n=1..30) ; # R. J. Mathar, Mar 04 2018

CROSSREFS

Cf. A272644.

Sequence in context: A217203 A052319 A127783 * A116539 A266467 A141318

Adjacent sequences:  A297192 A297193 A297194 * A297196 A297197 A297198

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane, Jan 10 2018

STATUS

approved

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Last modified March 19 23:02 EDT 2019. Contains 321343 sequences. (Running on oeis4.)